Intrinsic sensory disinhibition contributes to intrusive re-experiencing in combat veterans

Intrusive re-experiencing of traumatic events is a hallmark symptom of posttraumatic stress disorder (PTSD). In contrast to abstract, verbal intrusions in other affective disorders, intrusive re-experiencing in PTSD is characterized by vivid sensory details as "flashbacks". While prevailing PTSD models largely focus on dysregulated emotional processes, we hypothesize that deficient sensory inhibition in PTSD could drive overactivation of sensory representations of trauma memories, precipitating sensory-rich intrusions of trauma. In 86 combat veterans, we examined resting-state alpha (8-12 Hz) oscillatory activity (in both power and posterior-to-frontal connectivity), given its key role in sensory cortical inhibition, in association with intrusive re-experiencing symptoms. A subset (N = 35) of veterans further participated in an odor task (including both combat and non-combat odors) to assess olfactory trauma memory and emotional response. We observed a strong association between intrusive re-experiencing symptoms and attenuated resting-state posterior-to-frontal alpha connectivity, which were both correlated with olfactory trauma memory (but not emotional response). Importantly, olfactory trauma memory was further identified as a full mediator of the relationship between alpha connectivity and intrusive re-experiencing in these veterans, suggesting that deficits in intrinsic sensory inhibition can contribute to intrusive re-experiencing of trauma via heightened trauma memory. Therefore, by permitting unfiltered sensory cues to enter information processing and spontaneously activating sensory representations of trauma, impaired sensory inhibition can constitute a sensory mechanism of intrusive re-experiencing in PTSD.